The strongest domain is Biofuel.pro. This is definitely worth more than renewal fees. In the UK biofuel is becoming big business because high petrol prices are providing an incentive for people to buy used cooking oil from restaurants and convert it into biofuel for their cars. This cuts the cost of fuel by up to 75% and if you make less than 2,500 litres per year it's tax free. Put together a nice mini-site like this
http://biofuel.org.uk/ or market it to manufacturers, distributors and resellers of biofuel processor kits. They cost about £2,000 in the UK.
It surprises me that people with such forgettable and ugly .com and .net domains are so narrow minded about alternative extensions they might not have heard of. ddesign's best signature domain is probably HRwebsite.net. The key phrase "HR website" has 96,000 Google uniques. My .pro equivalent is Staff.pro. The single keyword staff has 543,000,000 Google uniques, that's 5000 times "HR website", the combination of keyword and extension "staff pro" has 78,000 Google unique, rising to 409,000 for "staff professional" and finally up to 4,830,000 for "professional staff".
If you are happy playing other people's games and registering the 78 millionth .com, then that's fine, but there will always be people who want something different and unique and are prepared to trek somewhere unexplored and put up with ridicule to find it.
The attitude of the people who own bad .coms today is no different to the attitude of the people who didn't know what the Internet was to people who registered .coms in the early 1990s. When somebody registered Sex.com everybody else thought it was worthless, just like they think .pro is worthless today.
If you put "mobile com" into Google you get 2,340,000 Google uniques, with "mobile pro" you get 23,100,000. The keyword mobile fits the extension .pro 10 ten times better than it fits .com. "Mobile info" has 194,000 Google uniques so mobile fits .pro 100 times better than it fits .info. You can carry on down through .mobi and .biz.